This research concerns the processes by which phage lambda is assembled, with emphasis on assembly processes which involve participation of molecules not found in the finished structure. We will purify and characterize the groE protein, a host-coded protein required for phage head assembly. We will purify various phage-coded proteins involved in assembly and search for interactions among them and with host-coded proteins such as groE. We will characterize the protein processing reactions (cleavage and fusion) that occur during lambda assembly by peptide mapping and sequencing techniques. We will study the detailed structure of the virion and its precurssor structures by chemical, immunological, and electron microscopic techniques.